Update wp-coding-standards/wpcs requirement from 3.0.1 to 3.1.0 (#246)

Updates the requirements on [wp-coding-standards/wpcs](https://github.com/WordPress/WordPress-Coding-Standards) to permit the latest version.
- [Release notes](https://github.com/WordPress/WordPress-Coding-Standards/releases)
- [Changelog](https://github.com/WordPress/WordPress-Coding-Standards/blob/develop/CHANGELOG.md)
- [Commits](WordPress/WordPress-Coding-Standards@3.0.1...3.1.0)

---
updated-dependencies:
- dependency-name: wp-coding-standards/wpcs
  dependency-type: direct:production
...

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composer.json

@@ -16,7 +16,7 @@
     "phpcompatibility/phpcompatibility-wp": "2.1.5",
     "sirbrillig/phpcs-variable-analysis": "2.11.18",
     "slevomat/coding-standard": "8.15.0",
-    "wp-coding-standards/wpcs": "3.0.1"
+    "wp-coding-standards/wpcs": "3.1.0"
   },
   "suggest": {
     "dealerdirect/phpcodesniffer-composer-installer": "Automatically adds this package's ruleset to the installed_paths option of PHP_CodeSniffer"